Abstract Clarix Imaging Corporation (Clarix) is focused on solving one of the largest problems in early stage breast cancer treatment, reoperations for positive margins. About 25% of the >200,000 patients who undergo lumpectomy in the US each year will face this additional procedure because current options for identifying positive margins intraoperatively are insufficient. Currently physicians rely on 2D specimen imaging for assessing margin status during surgery which cannot adequately represent the 3D margin morphology. Therefore, Clarix is developing a novel volumetric specimen imager, VSI, device that yields fully 3D images of the specimen with isotropic resolution which can significantly improve margin assessment and provide precise guidance for immediate re-excision before closing wound. We have previously demonstrated the ability of our VSI patented algorithms to overcome long scan times of conventional 3D imagers that would disrupt surgical workflow, and are now proposing development of a novel, algorithm-enabled spectral VSI system to further differentiate cancerous from healthy tissue. Recent developments by our founders allow for spectral CT with no special hardware. The addition of spectral imaging to our VSI system will enable automated cancer delineation in margin assessment improving surgical accuracy and pathologic assessment, and can also be applied to in vivo breast imaging. In the Phase I project we set out to demonstrate proof-of-concept of differentiation between breast tumors and healthy tissue using spectral image reconstruction tailored to VSI. The Specific Aims are to (1) create and validate simulated spectral VSI data of breast cancer specimens, (2) verify the robustness of the spectral VSI algorithm for breast cancer specimens, and (3) verify that spectral VSI can enable breast tumor delineation in patient specimens. Reaching the above Aims will firmly establish the feasibility of spectral CT for cancer differentiation further establishing Clarix VSI as the technical leader in the fast-growing specimen imaging market.